The present invention relates to a magnetic disc apparatus and loading method of a magnetic head for use in magnetic recording/reproducing systems which record and read out data on and from a magnetic recording medium.
FIG. 1 is a perspective view showing an arrangement of a conventional magnetic disc drive apparatus. In FIG. 1, illustrated at numeral 2 is a flexible member comprising a leaf spring one end portion of which is coupled to an arm 1. The flexible member 2 can flexibly be bent at the vicinity of the coupling portion to the arm 1 in a direction closer to a disc 5. At the top portion of the flexible member 2 there is provided a gimbal 3 which, as illustrated in FIG. 2, comprises a frame portion 3h and a tongue-like member 3i. At the vicinity of the top portion of the tongue-like member 3i there is formed a semi-spherical projection 3g which comes into contact with the flexible member 2. Illustrated at numeral 4 is a magnetic head which is fixedly secured to the tongue-like member 3i of the gimbal 3 and which is constructed as illustrated in FIG. 3. In FIG. 3, reference 4a represents a slider made of a magnetic material such as ferrite and provided with a U-shaped floating rail 4b generating a positive pressure and having a step portion 4c thereon. The reference 4d denotes a concave portion surrounded by the floating rail 4b where a negative pressure generates. Further, the references 4e and 4f are cores which are respectively connected to the slider 4a with non-magnetic materials 4g and 4h for acting as magnetic gaps being interposed therebetween. The core 4e is wound by a conductive wire 4i. Here, only the core 4e effects the magnetic recording and reproduction. Air flows from the sides indicated by characters A and C toward the sides indicated by characters B and D.
Returning again to FIG. 1, between the flexible member 2 and the disc 5 there is disposed a load pin 8 which is directly connected to a solenoid 9. The solenoid 9 moves load pin 8 up and down so as to cause the magnetic head 4 to be displaced toward the disc 5.
Operation of the conventional magnetic disc drive apparatus thus arranged will be described hereinbelow with reference to FIGS. 4A to 4C. In loading, the flexible member 2 is first lifted by the load pin 8 as illustrated in FIG. 4A so that the magnetic head 4 takes the state separated from the disc 5. Secondly, in response to supply of a current to the solenoid 9 after the disc 5 reaches a predetermined rotational speed, the load pin 8 moves so as to be closer to the disc 5. Since a load is applied to the flexible member 2 in the direction closer to the disc 5, the flexible member 2 flows the movement of the load pin 8 and moves toward the disc 5 so that the magnetic head 4 approaches the disc 5 as illustrated in FIG. 4B. When the magnetic head 4 further approaches the disc 5, a negative pressure generates with respect to the magnetic head 4 whereby the magnetic head 4 is drawn toward the disc 5 and floats as illustrated in FIG. 4C. In the floating state, the magnetic head 4 floats under the balance between the positive pressure, the negative pressure and the load of the flexible member 2, and takes the pitching and rolling actions about the projection 3g of the gimbal 3 so as to follow the movement such as vibration of the disc 5. Further, in the floating state, a current always flows through the electromagnetic solenoid 9 whereby the flexible member 2 does not come into contact with the load pin 8 even if the magnetic head 4 moves with respect to the data track on the disc 5 for recording or reproduction. In response to the completion of given recording or reproduction, the flexible member 2 moves up to the position of the load pin 8 and the rotational speed of the disc 5 decreases. In addition, the current to the solenoid 9 is cut whereby the solenoid 9 tends to return to the original position and at the same time the load pin 8 causes the flexible member 2 to separate from the disc 5 so that the magnetic head 4 is separated from the disc 5.
The magnetic disc drive apparatus thus arranged is designed such that the magnetic head 4 just floats on the disc 5 when the surface of the magnetic head 4 becomes parallel to the disc 5 in bringing the magnetic head 4 close to the disc 5. Further, in the case that the magnetic head 4 floats on the disc 5, the separation between the flexible member 2 and the disc 5 is about 1 mm, and in order for preventing the load pin 8 from coming into contact with the disc 5, the load pin 8 is required to be slenderized and hence the load pin 8 is arranged to have a thin-plate-like configuration or a thin-pin-like configuration. When the flexible member 2 is supported by the load pin 8, the load pin 8 is bent and the flexible member 2 is supported by the load pin 8 so as to be inclined along the load pin 8, because the flexible member 2 takes the state that approaches the disc 5. FIGS. 5A and 5B show these states.
FIG. 6 shows another conventional apparatus where a supporting member 10 is provided in place of the load pin 8 and the electromagnetic solenoid 9 and FIGS. 7A to 7C are illustrations for describing the operation of the FIG. 6 conventional apparatus. FIG. 7A shows the state that the disc 5 stops to rotate and the magnetic head 4 is separated from the disc 5. In FIG. 7A, the flexible member 2 is supported by the supporting member 10 and bent at the vicinity of the arm 1 in the direction closer to the disc 5. That is, the load is arranged to be applied in the direction that the flexible member 2 is brought closer to the disc 5. Further, the flexible member 2 is provided so as to be movable in the directions that traverses the data track of the disc 5. In response to moving to the inner circumference side of the disc 5, the flexible member 2 moves to slide on the supporting member 10 as illustrated in FIG. 7B. When further moving on the supporting member 10, the flexible member 2 is slid down therefrom so as to be displaced onto the disc 5 and at the same time the magnetic head 4 floats above the disc 5 as illustrated in FIG. 7C. After the completion of the recording or reproduction, the flexible member 2 moves toward the supporting member 10 so as to be put on the supporting member 10. At this time, the load is applied to the magnetic head 4 in the direction that separates from the disc 5, and the rotational speed of the disc 5 decreases and the magnetic head 4 returns to the original position (FIG. 7A).
This arrangement does not require that the supporting member 10 moves and does not require that the supporting member has a thin configuration unlike the first-mentioned conventional apparatus. However, as illustrated in FIG. 7B, immediately before the separation of the flexible member 2 from the supporting member 10, an eccentric force is applied to the flexible member 2 so that the flexible member 2 displaces in its width-direction so as to incline the magnetic head 4. In addition, after the separation of the flexible member 2 from the supporting member 10, the flexible member 2 rapidly displaces toward the disc 5 by its restoring force so that the magnetic head 4 approaches the disc 5 at an extremely high speed.
Here, the magnetic head 4 is brought closer to the disc 5 from the air-inlet side (A and C sides in FIG. 3) so that the magnetic head 4 moves in the direction perpendicular to the surface of the disc 5 within the region in which air flow occurs on the surface of the disc 5 by the rotation of the disc 5. This provides the possibility that the magnetic head 4 comes into contact with the disc 5 to damage the disc 5 because of no generation of a sufficient positive pressure.
Moreover, although the magnetic head 4 is designed so as to float on the disc 5 when the surface of the magnetic head 4 substantially becomes parallel to the surface of the disc 5, the space between the arm 1 and the disc is actually irregular due to the error in the machining accuracy of the arm 1 and the error in assembling whereby the air-inlet side (A, C in FIG. 3) of the magnetic head 4 can approach the disc 5 preceding the air-outlet side (B, D in FIG. 3) or vice versa. FIGS. 8A and 8B show this state. FIG. 8A shows the case that the error of the space between the arm 1 and the magnetic head 4 occurs such that the arm 1 approaches the disc 5, i.e., the case that the magnetic head 4 approaches the disc 5 from the air-inlet side, and FIG. 8B shows the case that the error therebetween occurs such that the arm 1 is separated from the disc 5, i.e., the case that the magnetic head 4 approaches the disc 5 from the air-outlet side. These states can also occur due to the other errors such as an error in thickness.
In a general magnetic disc drive apparatus, when the magnetic head 4 floats, the space between the magnetic gap of the magnetic head 4 and the disc 5 is set to be as extremely small as 0.1 to 0.2 microns, and therefore, for stably floating the magnetic head 4 above the disc 5, the magnetic head 4 is required to be substantially parallel to the disc 5 before floating and the positive pressure due to air flow caused by the rotation of the disc 5 acts as a force to parallel the magnetic head 4 with respect to the disc 5. However, when the inclination between the air-inlet side and the air-outlet side is extremely great, difficulty is encountered to parallel the magnetic head 4 with respect to the disc 5 whereby the magnetic head 4 comes into contact therewith.
In the first-mentioned conventional apparatus, in response to a current whose value is above a predetermined value, the solenoid 9 operates to cause the load pin 8 to approach the disc 5, and in response to a current whose value is below a predetermined value, the solenoid 9 operates to cause the load pin 8 to separate from the disc 5. At this time, the solenoid 9 operates at an extremely high speed so that the magnetic head 4 moves at the corresponding speed in the directions perpendicular to the disc 5. In the case that the magnetic head 4 approaches the disc 5 at an extremely high speed under the condition that the magnetic head 4 is inclined with respect to the disc 5, the magnetic head 4 can approach the disc 5 with a time period shorter than the time period taken for paralleling the magnetic head 4 by the positive pressure, thereby causing the magnetic head 4 to come into contact with the disc 5. Similarly, the second-mentioned conventional apparatus has the same problem because the flexible member 2 rapidly approaches the disc 5 by the spring force of the flexible member 2. In addition, in the case of the second-mentioned conventional apparatus, a load is always applied to the flexible member 2 in the direction that the magnetic head 4 approaches the disc 5 even after the magnetic head 4 has floated above the disc 5, and therefore there is the possibility that the magnetic head 4 is brought into contact with the disc 5 due to vibration of the arm 1 and the like. These problems do not permit data to be written at the head-loading area on the disc 5 but require a specific loading area on the disc 5 for preventing the previously written data from being broken.